1. Field of the Invention
This invention relates generally to fan motors used in air moving applications, such as in refrigeration apparatus, and more particularly to attachment of a fan blade to a motor shaft.
2. Description of the Prior Art
Shaded pole and capacitor induction motors have long been used for driving fans, such as condenser fans in refrigeration systems, the fan blade typically being connected directly to the rotor shaft. In one common type of fan motor, the rotor laminations are mounted on a die cast aluminum hub, the fan blade being in engagement with the end of the hub and maintained perpendicular to the shaft thereby. In that prior construction, the fan blade is secured on the shaft by a Speed Nut threaded on the end of the shaft and is driven by a drive pin located in a hole drilled in the end of the hub.
Shaded pole and capacitor fan motors are now available, such as those described in my Pat. No. 4,045,698, in which the hub of the rotor is too small adequately to maintain the fan blade perpendicular to the motor shaft and further, since the hub is made of steel rather than die cast aluminum, it does not serve to conduct the rotor heat to the aluminum fan as well as the larger, aluminum hub of the prior motors. It is therefore desirable to provide a frictional fan blade attachment which will maintain the requisite perpendicular relationship of the fan blade with the shaft without relying on engagement with the rotor hub, which will provide good conductivity of rotor winding heat to the fan blades, and which eliminates the threaded shaft end, speed nut and drive pin employed in prior motors. Frictional drive of the fan blade not only eliminates the difficult-to-watch fan blade drive pin hole and drive pin, but also eliminates the possibility of loosening the retaining nut which can happen in case a small amount of rotation occurs between the nut and shaft, or in the case of a reversible motor.